1. Field of the Invention
This invention pertains to a particular arrangement of control equipment such as humidistats and control relays to enable a conventional heating and air conditioning unit to provide a dehumidification feature without the addition of reheat equipment and without the necessity of extensive system modifications.
2. Description of the Prior Art
Prior heating and air conditioning units which were able to provide a humidity control feature included a gas or electric downstream duct heater that reheated the cooled air exiting from the dehumidifying evaporator of the air conditioning unit. Because air must be cooled to its dew point to remove moisture, the air from which moisture has been removed is objectionably cool and therefore it is undesirable to feed such cool air into a room where a draft and associated chill may be produced. Thus in any dehumidification system, after the air had been cooled to its dew point to allow moisture to condense out the air would then be fed through a relatively small reheat unit which would raise the temperature of the air from generally in the vicinity of 45.degree. to 55.degree. to in the vicinity of 68.degree. to 70.degree. which is comfortable. The reheat equipment thus used was matched to the air conditioning equipment and only sufficient to raise the temperature of dehumidified air to a comfortable level. The reheat equipment was not sufficient to provide heating alone which would be provided by a much larger heating chamber and plenum generally located upstream of the reheat equipment. Because of the requirement for a primary heating unit and the necessity of a separate reheat element, dehumidification equipment is oftentimes omitted except from the most elaborate or humidity sensitive areas. With this circuitry of this invention, the addition of a few control circuit components will enable a conventional heating and air conditioning unit, such as a rooftop unit, to provide a dehumidifying feature.